We measure the transmission of O6+ ions with a higher energy of 60 keV (in turn a higher value of Ep/q) through capillaries in an uncoated Al2O3 membrane, and obtain agreements with previously reported results in general angular distribution of the transmitted ions and the transmission profile width variation with capillary tilt angle.
The transmission fractions as a function of the tilt angle can be fitted to the semi-empirical Gaussian-like function well. Due to using uncoated capillary membrane, our ψc is larger than that using gold-coated one, in spite of our larger value of Ep/q, which suggests a larger equilibrium charge Q∞ in our experiment.